Combustion method using ammonia-containing fuel

Abstract

To provide a combustion method using ammonia-containing fuel that minimizes carbon dioxide emissions during co-firing of ammonia with fossil fuels, contributes to carbon neutrality, suppresses NOx generation, and reduces the generation of unburned ammonia. [Solution] In a combustion method using a fuel containing ammonia, first the mixing ratio of ammonia is set to 0% and the mixing ratio of fuels other than ammonia is set to 100%, primary combustion air is supplied in proportion to the fuel supply amount, and the burner combustion air ratio ε is adjusted so that ε > 1.0, then the mixing ratio of fuels other than ammonia is changed from 100% to 0%, and the mixing ratio of ammonia is changed from 0% to 100%, so that the burner combustion air ratio ε is 0.7

Description

Technical Field

[0005] , , ,

[0001] The present invention relates to a combustion method using a fuel containing ammonia. Specifically, it relates to a combustion method using a fuel containing ammonia that can ensure the ignition and combustion stability of ammonia, suppress the emission of carbon dioxide, suppress the emission of NOx, and suppress the generation of unburned ammonia.

Background Art

[0002] Ammonia has attracted attention as a carbon-neutral fuel because it does not emit carbon dioxide, which is a greenhouse gas. However, ammonia has problems such as a slow combustion rate and poor ignition and combustibility. Therefore, technologies for solving the above problems by co-firing with fossil fuels and the like are known (Patent Documents 1 and 2).

[0003] In addition, since ammonia is a nitrogen-containing substance, in view of the fact that a large amount of NOx, which is a harmful substance, is generated during combustion, in the previous stage of ammonia combustion, the combustion air is supplied less than the required amount to suppress the generation of NOx by reducing combustion, and a two-stage combustion method of supplying the insufficient combustion air in the latter stage is known (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional technologies that co-fire ammonia with fossil fuels produce carbon dioxide, which is a problem as it prevents achieving sufficient carbon neutrality. Furthermore, co-firing ammonia with fossil fuels tends to generate more NOx than burning ammonia alone, which poses a significant problem from the perspective of preventing air pollution.

[0006] Patent Document 2 describes a two-stage combustion process for ammonia co-firing. In the first stage of combustion, it is disclosed that the system operates with a theoretical air amount / fuel supply amount = air ratio (λ), and that it operates under the condition λ < 1, specifically 0.6 < λ < 0.9, performing ammonia combustion in a reducing atmosphere. However, when the reducing effect is high in a reducing atmosphere (low combustion air), a large amount of unburned ammonia is generated, which is a drawback.

[0007] Therefore, the object of the present invention is to provide a combustion method using a fuel containing ammonia that can minimize the generation of carbon dioxide even when ammonia is co-fired with fossil fuels, contribute to carbon neutrality, suppress the generation of NOx, and suppress the generation of unburned ammonia.

[0008] Furthermore, other problems of the present invention will become clear from the following description. [Means for solving the problem]

[0009] The above problems are solved by the following inventions.

[0010] (Claim 1) In a combustion method using ammonia-containing fuel, in which a combustion furnace equipped with a burner is burned with the ammonia-containing fuel in the burner to generate hot air, In a combustion method using a fuel containing ammonia, in which high-temperature gas of hot air generated by the burner is introduced into a combustion furnace, During the process from the startup to steady-state operation of the aforementioned combustion furnace, (1) In the first stage of starting up the operation, The mixing ratio of ammonia is set to 0%, and the mixing ratio of fuels other than ammonia is set to 100%. When supplying primary combustion air in proportion to the fuel supply amount for burner combustion, and the burner combustion air ratio ε = supply air amount / theoretical air amount of fuel, the burner combustion air ratio ε is adjusted so that ε > 1.0. (2) In the second stage, from the first stage during startup to the steady-state operation, The mixing ratio of fuels other than ammonia is changed from 100% to 0%, while the mixing ratio of ammonia is changed from 0% to 100%. The burner combustion air ratio ε is adjusted so that 0.7 < ε < 1.0. (3) In the third stage, which is the entry into steady-state operation after the second stage, The mixing ratio of fuels other than ammonia is set to 0%, and the mixing ratio of ammonia is set to 100%. A combustion method using a fuel containing ammonia, characterized in that the burner combustion air ratio ε is adjusted so that 0.9 < ε < 1.0. (Claim 2) The combustion method using a fuel containing ammonia according to claim 1, characterized in that, in the third stage, the fuel is 100% ammonia-burned, the burner combustion air ratio ε is adjusted to 0.9 < ε < 1.0, and the combustion furnace temperature is further adjusted to 900°C to 1100°C. (Claim 3) The combustion method using a fuel containing ammonia according to claim 2, characterized in that the burner combustion air ratio ε is adjusted to 0.96 < ε < 0.99. (Claim 4) A combustion method using a fuel containing ammonia according to claim 1, characterized in that secondary combustion air for combustion is supplied to the combustion furnace. (Claim 5) The system includes a branching channel for branching the supply path of fuel ammonia supplied to the burner, The combustion method using a fuel containing ammonia according to claim 1, characterized in that a portion of the fuel ammonia is supplied to the combustion furnace as a reducing agent from the branched channel. (Claim 6) The combustion method using a fuel containing ammonia according to claim 1, characterized in that the primary combustion air is swirled and supplied from the side surface of the burner.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a combustion method using a fuel containing ammonia that suppresses the generation of unburned ammonia and ensures the ignition and combustion sustainability of ammonia.

[0012] According to the present invention, when the fuel other than ammonia is a fossil fuel, by limiting its use only during temperature rise, it is possible to provide a combustion method using a fuel containing ammonia that contributes to carbon neutrality by limiting carbon dioxide emissions to a minimum. Further, according to the present invention, when the fuel other than ammonia is hydrogen, it is possible to provide a combustion method using a fuel containing ammonia that contributes to carbon neutrality without emitting carbon dioxide during combustion.

Brief Description of the Drawings

[0013] [Figure 1] A diagram showing an example of a combustion apparatus for implementing the combustion method using a fuel containing ammonia of the present invention [Figure 2] A diagram showing an example of a combustion furnace of the present invention [Figure 3] A diagram showing Test Data 1 [Figure 4] A diagram showing Test Data 2 [Figure 5] A diagram showing Test Data 3

Modes for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described. <0,

[0015] The combustion method using ammonia-containing fuel of the present invention is carried out by a combustion furnace using ammonia-containing fuel, which comprises a burner that burns ammonia-containing fuel to generate hot air, and a furnace body that introduces high-temperature gas from the burner to burn materials to be incinerated, including waste liquid and waste gas (drainage liquid and exhaust gas). An example of the combustion apparatus will be explained with reference to Figures 1 and 2.

[0016] Figure 1 shows an example of a combustion apparatus according to the present invention, and Figure 2 shows an example of a combustion furnace according to the present invention. In Figures 1 and 2, a vertical combustion furnace 1 is used in this embodiment. The combustion furnace 1 has a burner 2 at the top and a furnace body 3 below the burner 2. The lower part of the burner 2 is open and connected to the furnace body 3. A fuel containing ammonia is burned to generate hot air.

[0017] The combustion furnace 1 uses a burner 2 to introduce and burn high-temperature gas, sending flame and heat to the furnace body 3. The flame forms a swirling flow. Combustion furnace 1 can also be used as a hot blast furnace without supplying waste liquids or exhaust gases to be incinerated, if there are no materials to be incinerated, including waste liquids or exhaust gases, to be introduced into the furnace body described later.

[0018] As shown in Figure 2, the burner 2 is equipped with a burner nozzle 20, and a pipe 21 for supplying ammonia fuel is connected to the burner nozzle 20. In addition, a pipe 22 for supplying fuels other than ammonia is connected to pipe 21 and configured to supply them to the burner nozzle 20.

[0019] In this embodiment, it is preferable that the piping 21 is provided with a first flow rate control means 210 for controlling the supply amount of ammonia, and the piping 22 is provided with a second flow rate control means 220 for controlling the supply amount of fuel other than ammonia. The first flow rate control means 210 and the second flow rate control means 220 can be exemplified by solenoid valves, for example, and the flow rate can be controlled by adjusting the opening degree of the valves. In addition to solenoid valves, air-driven valves can also be used, but the invention is not limited to these.

[0020] In this embodiment, it is preferable that the piping 21 is equipped with an on / off valve (not shown) in addition to the first flow rate control means 210, and it is also preferable that the piping 22 is equipped with an on / off valve (not shown) in addition to the second flow rate control means 220.

[0021] In this embodiment, it is preferable that the piping 21 is provided with a first flow rate measuring means 211 for measuring the supply flow rate of ammonia, and the piping 22 is provided with a second flow rate measuring means 221 for measuring the supply flow rate of fuels other than ammonia. The first flow rate measuring means 211 and the second flow rate measuring means 221 can be flow meters capable of measuring the supply flow rate of fuels.

[0022] Other fuels besides ammonia include hydrogen and fossil fuels. Fossil fuels include heavy oil, kerosene, natural gas, and LPG (petrochemical gas). The following explanation will focus on the case where LPG is used as the fuel other than ammonia.

[0023] It is preferable that the burner 2 is equipped with a swirling mechanism (not shown). By making the flame a short flame using such a swirling mechanism, interference with the waste liquid and exhaust gas in the combustion device 1 is prevented, thereby preventing incomplete combustion, suppressing the generation of carbon monoxide, and enabling safe combustion treatment of the waste liquid and exhaust gas.

[0024] A portion of the ammonia can be supplied to the furnace body 3 via a branch channel 30 that branches off the supply path of the ammonia supply piping 21, and used as a reducing agent. Preferably, the branch channel 30 is provided with an on-off valve 300 that can be opened and closed as needed. This supply can complement NOx suppression. This eliminates the need to prepare a new reducing agent, contributing to cost reduction. In this embodiment, it is also preferable to provide a reducing agent flow control valve 301 to supply ammonia as a reducing agent according to the measured NOx value, for example. This makes it possible to more reliably complement NOx suppression and supply an appropriate amount of ammonia. In this embodiment, either the on-off valve 300 or the flow control valve 301, or both, can be used, as long as an appropriate amount of reducing agent necessary to complement NOx suppression is supplied. Furthermore, it is also preferable to provide a flow rate measuring means 302 for measuring the flow rate of ammonia supplied from the branch channel 30.

[0025] The burner 2 is supplied with primary combustion air via an air pipe 23. Preferably, the air pipe 23 is provided with an air supply adjustment means 230, which allows adjustment of the amount of primary combustion air supplied. The air pipe 23 is also provided with an air supply measuring means 231 for measuring the amount of primary combustion air supplied. The air supply measuring means 231 can be any measuring instrument capable of measuring the flow rate of primary combustion air. In this embodiment, the amount of primary combustion air supplied is calculated based on the burner combustion air ratio ε, which will be described later, and the theoretical air amount of the fuel.

[0026] In the above, the primary combustion air and secondary combustion air are supplied from a blowing means 10 such as a blower or compressor.

[0027] Waste liquid and waste gas are supplied to the furnace body 3 via the incineration piping 31. Secondary combustion air is supplied to the furnace body 3 via the secondary combustion air piping 32. The secondary combustion air may also be supplied via the incineration piping 31.

[0028] In this embodiment, the control unit 11 is connected to a first flow rate control means 210, a first flow rate measuring means 211, a second flow rate control means 220, and a second flow rate measuring means 221 in order to adjust the supply flow rate of fuels such as ammonia fuel and fuels other than ammonia, and the supply flow rate of each fuel can be adjusted. Furthermore, the control unit 11 is connected to a blower 10 and an air supply adjustment means 230. By controlling the total amount of air supplied from the blower 10 and adjusting the opening of the air supply adjustment means 230, the supply amounts of primary and secondary combustion air can also be controlled. In this embodiment, a secondary combustion air adjustment means (not shown) may be provided in the secondary combustion air piping 32, and the control unit 11 may adjust the amount of secondary combustion air supplied. Furthermore, in this embodiment, the control unit 11 can also adjust the opening degree of the flow control valve 301 based on the flow rate measured by the flow rate measuring means 302 to supply an appropriate amount of ammonia as a reducing agent.

[0029] As shown in Figure 1, the combustion gases inside the furnace body 3 are discharged from the discharge section 4 into the cooler 5. The cooler 5 is filled with water 50 to a certain height. The outlet of the discharge pipe 40 extends into the water 50 so that the combustion gases can be discharged into it.

[0030] The combustion gas is cooled as it passes through the water 50 and sent to the scrubber 6 via the piping 51. The scrubber 6 is equipped with a cleaning section 60 and a tank 61. The combustion gas sent from the piping 51 is cleaned in the cleaning section 60, and the cleaned combustion gas is sent to the chimney 7 via the piping 62. The cleaning water used for cleaning is stored in the tank 61 and can be circulated via the circulation pump 8 as cooling water for the cooler 5 and cleaning water for the scrubber 6. If the water in the tank 61 is insufficient, it is preferable to replenish it with makeup water to maintain a predetermined level.

[0031] The water 50 in the cooler can 5 becomes contaminated as combustion gases pass through from the discharge port, so the water can be treated from the cooler can 5 using the discharge pump 9. Also, the cleaning water in the scrubber 6's tank 61 becomes contaminated during the cleaning process, so the water can be treated from the tank 61 using a discharge pump (not shown).

[0032] Next, a preferred embodiment of a combustion method using a fuel containing ammonia will be described.

[0033] The combustion method using ammonia-containing fuel is applied to a method in which ammonia-containing fuel is burned in a burner section to generate hot air, and the high-temperature gas of the hot air generated in the burner section is introduced into the furnace body to burn the material to be incinerated.

[0034] The combustion method shown in Figures 1 to 4 of Patent Document 2 comprises a first combustion chamber (21) and a second combustion chamber (22). In the first combustion chamber (21), a fuel F containing ammonia and a first-stage combustion air (11) is supplied to the burner (5).

[0035] The first combustion chamber (21) is supplied with first-stage combustion air (11) at a supply amount such that the air-fuel ratio (λ1) to the supplied fuel F is (λ1). The air-fuel ratio (λ1) is between 0.6 and less than 0.9. Since λ1 < 0 in the first combustion chamber (21), it is a reducing atmosphere (low-oxygen atmosphere), and therefore the generation of NOx due to the combustion of ammonia is suppressed.

[0036] However, in the first combustion chamber (21), even if all the first-stage combustion air (11) reacts, some of the fuel F remains unburned. Therefore, in the first combustion chamber (21), a high-temperature gas is generated, which is a mixture of the burnt gas produced by the combustion of fuel F and the unburned portion of fuel F. This high-temperature gas flows into the second combustion chamber (22) through the throttling section (23), and first meets the second-stage combustion air (12) blown out from the second-stage combustion air nozzle (26) of the intermediate nozzle section (39) in the NOx suppression combustion zone (37). Patent Document 2 states that unburned components in the high-temperature gas are burned by oxygen contained in the air for two-stage combustion (12).

[0037] In contrast, according to the present invention, by appropriately adjusting the combustion air ratio in the burner for each combustion pattern, such as mixed combustion of fuels other than ammonia (fossil fuels, etc.) and ammonia, and for ammonia-only combustion, NOx generation is suppressed at all combustion stages from temperature rise to stable combustion.

[0038] This invention employs a three-stage switching combustion method as shown in Table 1.

[0039] [Table 1]

[0040] The three-stage switching combustion method shown in Table 1 was developed by acquiring NOx data at each stage, analyzing that data, and finding the optimal operating method, which led to the present invention. The combustion data assumes the combustion of industrial waste, and since the NOx regulatory limit for waste incineration facilities is 250 ppm (calculated as 12% O2), it is essential for the NOx value to be below this regulatory limit for performance reasons.

[0041] <Phase 1> (1) During the initial burner startup, combustion is performed in an oxidizing atmosphere without using ammonia fuel (ammonia mixture ratio 0%), using a fossil fuel other than ammonia (fossil fuel mixture ratio 100%), so that the burner combustion air ratio ε, calculated as supply air amount / theoretical air amount of fuel = ε, is ε > 1.0.

[0042] As shown in Figure 2, the first flow rate control means 210 is fully closed, and the second flow rate control means 220 is adjusted to a predetermined opening. The control unit 11 can calculate the theoretical amount of fuel air based on the supply flow rate of fuels other than ammonia measured by the second flow rate measuring means 221. After calculating the theoretical amount of fuel air, the control unit 11 can calculate the supply air amount based on a preset combustion air ratio ε, and adjust the opening of the blower means 10 and the supply air adjustment means 230 based on the calculated supply air amount. The above explanation describes a case where the burner combustion air ratio ε is pre-set, but it is also possible to change this setting. In this case, since the stoichiometric air-fuel ratio of the fuel has been calculated, the amount of air supplied can be varied by changing the burner combustion air ratio ε.

[0043] At this stage, the temperature is raised by stable combustion using fossil fuels in an oxidizing atmosphere, and the inside of the combustion furnace is heated by stable combustion. Since no ammonia is added, the problem of unburned ammonia does not occur, and there is no generation of NOx due to ammonia.

[0044] The first stage [Test Data 1] is shown in Figure 3. For data on fossil fuel-fired combustion, combustion data was obtained for LPG-fired combustion. Figure 3, [Test Data 1], also shows data measuring NOx values ​​when the ratio of fuel supplied to the second-stage burner, which will be described later, was changed from 100% LPG to 100% NH3.

[0045] Figure 3, [Test Data 1], shows operating data for oxidative combustion, reductive combustion, and in-furnace denitrification (a method of supplying ammonia to the furnace body as a reducing agent for NOx reduction). Oxidative combustion is an operation in which the entire amount of primary combustion air is supplied to the burner. Reductive combustion is an operation in which primary combustion air is supplied to the burner section so that the air-to-burn ratio ε is less than 1 (ε<1), and the remaining secondary air is supplied to the furnace body.

[0046] Basically, the air supplied to the burner section and the furnace body is operated so that the air-fuel ratio ε is approximately 1.2 in all operating patterns. For example, as explained in the example in Figure 2, by controlling the total amount of air supplied by the blower 10 so that the air ratio ε is 1.2 and adjusting the opening of the supply air adjustment means 230, the amount of primary combustion air supplied can be adjusted so that the air ratio ε is 0.8 and the air ratio ε of secondary combustion air is 0.4.

[0047] In the reduction combustion described in [Test Data 1], the primary combustion air ratio ε supplied to the burner section was set to 0.8, the secondary combustion air ratio to 0.4, and the combustion furnace was operated so that the overall combustion air ratio was 1.2. Furthermore, [Test Data 1] includes one data point each for oxidative combustion and reductive combustion when using LPG exclusively, and the NOx values ​​for fossil fuel combustion are sufficiently low.

[0048] <Phase 2> Intermediate stage leading to steady-state operation of the combustion furnace After confirming that the temperature inside the combustion furnace has stabilized within a predetermined temperature range, such as by maintaining the temperature within the combustion furnace within a predetermined temperature range for a predetermined time, the fossil fuels are switched to ammonia. In order to suppress the generation of NOx at this time, the primary combustion air ratio (burner combustion air ratio) ε supplied to the burner is set to less than 1 (ε<1) for reduction combustion, and secondary combustion air is supplied to the furnace body, where the combustion air ratio is set to greater than 1 (ε>1), preferably greater than 1.1 (ε>1.1).

[0049] In this case, the control unit 11 can calculate the theoretical amount of air for the fuel based on the supply flow rate of ammonia fuel measured by the first flow rate measuring means and the supply flow rate of fuel other than ammonia measured by the second flow rate measuring means. Furthermore, once the theoretical amount of air for the fuel is calculated, the control unit 11 can calculate the amount of supply air based on a preset combustion air ratio ε, and adjust the airflow rate of the blower 10 and the opening degree of the supply air adjustment means 230 based on the calculated amount of supply air. The above explanation describes a case where the burner combustion air ratio ε is pre-set, but it is also possible to change this setting. In this case, since the stoichiometric air-fuel ratio of the fuel has been calculated, the amount of air supplied can be varied by changing the burner combustion air ratio ε.

[0050] In combustion at the burner, increasing the reduction level can lead to unstable combustion and misfires; therefore, the primary combustion air ratio should exceed 0.7. That is, it should be adjusted so that 0.7 < ε < 1.0. Furthermore, since the generation of N2O can be suppressed by setting the primary combustion air ratio to more than 0.8, it is preferable to adjust the primary combustion air ratio so that 0.8 < ε < 1.0. The mixing ratio of fuels other than ammonia is changed from 100% to 0% by a second flow rate control means, and the mixing ratio of ammonia is changed from 0% to 100% by a first flow rate control means. Once the temperature inside the combustion chamber reaches a high and stable level, the fossil fuels will be switched to ammonia.

[0051] Data on the co-firing of fossil fuels and ammonia in the second phase is also included in the aforementioned [Test Data 1], so you can refer to that. The co-firing patterns will have three LPG:ammonia ratios: 75:25, 49:51, and 29:71. The co-firing ratio is expressed as a ratio of calorific value. Of the three data sets, the 75:25 pattern represents reductive combustion, with NOx levels below 250 ppm. However, the remaining two also show reductive combustion, with significantly lower NOx levels compared to oxidative combustion, but still slightly above 250 ppm.

[0052] Regarding this, in the following ammonia-only combustion data, the NOx values ​​for co-firing (289 ppm, 312 ppm) were lower than those for ammonia-only combustion (481 ppm) in a comparison with reductive combustion. Furthermore, in the operation of ammonia-only combustion with reductive combustion, the NOx values ​​were sufficiently reduced (203 ppm, 87 ppm). Therefore, it is considered that NOx can be sufficiently reduced in co-firing as well by combining reductive combustion and in-furnace denitrification.

[0053] <Phase 3> (3) During the steady-state operation phase of the combustion furnace, During this steady-state operation phase, the primary combustion air ratio (burner combustion air ratio) ε is adjusted so that 0.9 < ε < 1.0, the second flow rate control means is adjusted so that the mixing ratio of fuels other than ammonia is 0%, and the first flow rate control means is adjusted so that the mixing ratio of ammonia is 100%. The above operation method can efficiently suppress the generation of NOx.

[0054] Since the primary combustion air ratio is ε < 1.0, combustion occurs in a reducing atmosphere. However, because the lower limit is 0.9 < ε, the degree of reduction is relatively mild, and unburned ammonia at the burner outlet is suppressed. Furthermore, by adjusting the temperature of NOx and ammonia generated in the burner section to 900°C to 1100°C within the furnace body, the residue of unburned ammonia and NOx in the combustion gas at the furnace outlet can be significantly reduced and suppressed.

[0055] By adjusting the primary combustion air ratio (burner combustion air ratio) ε to preferably 0.96 < ε < 0.99, the degree of reduction becomes even milder, and unburned ammonia at the burner outlet is further suppressed.

[0056] The control unit 11 has a theoretical air amount for ammonia fuel stored in advance, and can calculate the amount of air to be supplied based on a preset burner combustion air ratio ε and the stored theoretical air amount for the fuel. Based on the calculated amount of air to be supplied, the amount of air supplied by the blower 10 and the opening degree of the supply air adjustment means 230 can be adjusted. The above explanation describes a case where the burner combustion air ratio ε is pre-set, but it is also possible to change the setting. In this case, since the stoichiometric air-fuel ratio of the fuel is stored in advance, the amount of air supplied can be varied by changing the burner combustion air ratio ε.

[0057] In the third stage of ammonia-only combustion, [Test Data 1] shows that NOx can be sufficiently suppressed by combining reductive combustion with in-furnace denitrification.

[0058] Furthermore, tests were conducted to confirm the NOx reduction effect efficiently using ammonia-only combustion (reductive combustion only), and experiments were carried out by changing the ratio of primary air supplied by the burner. The results of these tests are shown in Figure 4 [Test Data 2].

[0059] From test data 2, in the combustion method using only reduction combustion, NOx (calculated as 12% O2) was slightly above 250 ppm at a burner combustion air ratio of 0.8, slightly below 250 ppm at a burner combustion air ratio of 0.9, and sufficiently low at less than half of 250 ppm at a burner combustion air ratio of 0.98. On the other hand, NOx (calculated as 12% O2) was significantly above 250 ppm when the burner combustion air ratio was set to 1.1 and 1.2. Therefore, in ammonia-only combustion, NOx can be reduced by reduction combustion alone when the burner combustion air ratio is 0.9 < ε < 1.0, and preferably in the range of 0.96 < ε < 0.99.

[0060] [Ammonia decomposition rate, and other supplementary information] The ammonia decomposition rate after combustion was 99.99 to 99.999% in all of the above operating patterns, which suggests that sufficient decomposition performance was generally achieved.

[0061] In ammonia-only combustion, a burner-air ratio of slightly less than 1 (ε=0.98) is very effective in reducing NOx emissions. We conducted tests to confirm whether this effect is also present in mixed combustion. The result is shown in Figure 5 [Test Data 3]. Based on the results shown in Figure 4 (Test Data 2) and Figure 5 (Test Data 3), it can be concluded that a sufficient NOx reduction effect cannot be obtained with a burner air ratio of slightly less than 1 (ε=0.98) in mixed combustion, and that this method is only effective when ammonia is used exclusively for combustion.

[0062] In the present invention, if NOx cannot be completely suppressed by the above three-stage control, it is also possible to supplement NOx control by providing a branching channel that branches the fuel ammonia supplied to the burner, and supplying a portion of the combustion ammonia from the branching channel to the combustion furnace as a reducing agent. Because this method involves the partial supply of fuel ammonia, it can be implemented without using a new reducing agent (catalytic denitrification).

[0063] Furthermore, the above-mentioned burner improves flammability by rapidly mixing ammonia with combustion air by supplying primary combustion air from the side of the burner in a swirling manner. At the same time, the swirling motion prevents the diffusion of ammonia fuel, thus shortening the flame (short flame).

[0064] By utilizing a swirling mechanism in the burner to create a short flame, interference with waste liquids and exhaust gases in the combustion furnace is prevented, thereby preventing incomplete combustion, suppressing the generation of carbon monoxide, and enabling the safe combustion of materials to be burned (e.g., waste liquids and exhaust gases). This prevents interference with waste liquids and exhaust gases supplied from the combustion furnace, suppressing incomplete combustion between ammonia fuel and waste liquids and exhaust gases, and reducing the generation of unburned ammonia and carbon monoxide.

[0065] Furthermore, according to the present invention, the generation of unburned ammonia can be suppressed and NOx emissions can be suppressed due to the effect of the swirling flow (utilization of a swirling mechanism).

[0066] According to the present invention, the ignition and flammability of ammonia can be ensured. Ammonia is a flame-retardant substance, and if combustion is attempted at 100% from the low temperature rise stage of the combustion furnace, combustion will not be stable and a large amount of unburned ammonia will be generated. Therefore, by using other fuels with high calorific value (such as fossil fuels) during the heating phase and gradually switching from these other fuels (such as fossil fuels) to ammonia, it is possible to transition to 100% ammonia combustion while ensuring stable combustion.

[0067] Furthermore, it becomes possible to reduce CO2 and CO emissions. If other fuels are fossil fuels, limiting their use to only the heating phase can minimize carbon dioxide emissions and contribute to carbon neutrality.

[0068] Furthermore, by utilizing the swirling mechanism in the burner described above, the flame is shortened, preventing interference with waste liquid and exhaust gas in the combustion furnace, thereby preventing incomplete combustion, suppressing the generation of carbon monoxide, and enabling safe treatment of waste liquid and exhaust gas. In other words, by appropriately adjusting the combustion air ratio in the burner for each combustion pattern—exclusive combustion of other fuels (fossil fuels, etc.), mixed combustion of other fuels and ammonia, and exclusive combustion of ammonia—it becomes possible to suppress NOx generation at all combustion stages, from temperature rise to stable combustion.

[0069] Furthermore, by supplying a portion of the fuel ammonia in a divided manner and using it as a reducing agent, NOx suppression can be supplemented. Because the fuel ammonia is supplied in a divided manner, there is no need to prepare a new reducing agent. [Explanation of Symbols]

[0070] 1: Combustion device 2: Burner 20: Burner Nozzle 21: Piping 210: First flow rate control means 211: First flow rate measuring means 22: Piping 220: Second flow rate control means 221: Second flow rate measuring means 23: Air tube 230: Supply air adjustment means 231: Supply air measuring means 3: Combustion furnace 30: Branch channel 300: Shut-off valve 301: Flow control valve 302: Flow rate measurement means 31: Incineration piping 32: Secondary combustion air piping 4: Discharge section 40: Discharge pipe 5: Cooling can 50:Water 51: Piping 6: Scrubber 60: Cleaning section 61: Tank 62: Piping 7: Chimney 8: Circulation pump 9: Discharge pump 10: Blower means 11: Control Unit

Claims

1. In a combustion method using ammonia-containing fuel, in which a combustion furnace equipped with a burner is burned with the ammonia-containing fuel in the burner to generate hot air, In a combustion method using a fuel containing ammonia, in which high-temperature gas of hot air generated by the burner is introduced into a combustion furnace, During the process from the startup to steady-state operation of the aforementioned combustion furnace, (1) In the first stage of starting up the operation, The mixing ratio of ammonia is set to 0%, and the mixing ratio of fuels other than ammonia is set to 100%. When supplying primary combustion air in proportion to the fuel supply amount for burner combustion, and the burner combustion air ratio ε = supplied air amount / theoretical air amount of fuel, the burner combustion air ratio ε is adjusted so that ε > 1.

0. (2) In the second stage, from the first stage during startup to the steady-state operation, The mixing ratio of fuels other than ammonia is changed from 100% to 0%, while the mixing ratio of ammonia is changed from 0% to 100%. The burner combustion air ratio ε is adjusted so that 0.7 < ε < 1.

0. (3) In the third stage, which is the entry into steady-state operation after the second stage, The mixing ratio of fuels other than ammonia is set to 0%, and the mixing ratio of ammonia is set to 100%. A combustion method using a fuel containing ammonia, characterized in that the burner combustion air ratio ε is adjusted so that 0.9 < ε < 1.

0.

2. The combustion method using a fuel containing ammonia according to claim 1, characterized in that, in the third stage, the fuel is 100% ammonia-burned, the burner combustion air ratio ε is adjusted to 0.9 < ε < 1.0, and the combustion furnace temperature is further adjusted to 900°C to 1100°C.

3. The combustion method using a fuel containing ammonia according to claim 2, characterized in that the burner combustion air ratio ε is adjusted to 0.96 < ε < 0.

99.

4. The combustion method using a fuel containing ammonia according to claim 1, characterized in that secondary combustion air for combustion is supplied to the combustion furnace.

5. The system includes a branching channel for branching the supply path of fuel ammonia supplied to the burner, The combustion method using a fuel containing ammonia according to claim 1, characterized in that a portion of the fuel ammonia is supplied to the combustion furnace as a reducing agent from the branched channel.

6. The combustion method using a fuel containing ammonia according to claim 1, characterized in that the primary combustion air is supplied in a swirling manner from the side of the burner.

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